Science Scoops: Does Having Boys or Girls Run in the Family?

by Stephen James O'Meara

Let's say you are a girl who comes from a family of all girls. Does that mean that you, too, have a high probability of bringing a girl into the world? No. In fact, statistical theory suggests otherwise. According to Chance magazine (published by the American Statistical Association), there is no compelling evidence to suggest that family history plays a role in whether a family has male or female children.

The fact is, statistically, around one-eighth of all four-child families are expected to be all-male or all-female under a chance model. And it's possible, statistically, for families of up to 10 children to be all of the same sex. There is no evidence that having boys (or girls) has either genetic or shared environmental sources of influence.

Vocabulary

genetic: Of or relating to the branch of biology that deals with how characteristics are passed from parents to offspring.

statistical: Relating to a collection or set of numbers, facts, or other data.

Activity

Some traits are inherited, or passed along, from parents to their children. Other traits are acquired, or learned by an organism after it is born. Think of five things that you do in your life that you learned how to do by watching or learning from someone else. Print out the chart and write one trait at the top of each column. Beneath each trait, circle “Learned on My Own” if you learned this trait on your own or “Someone Taught Me” if you learned this trait because someone else taught it to you. If someone else taught you the trait, write down that person's name.[anno: Answers will vary.]